The closed cavity method is proposed to measure the frequency temperature coefficient (τ_f) of a dielectric resonator. The τ_f polynomial, which is linear combination of the temperature coefficient of relative dielectric constant and the linear expansion coefficient of the dielectric and cavity, is given. The coefficients of τ_f polynomial are discussed in detail. The intrinsic temperature coefficient of resonant frequency (τ_f0) is introduced to improve the measurement precision. Resonators made of BaO-TiO₂-Sm₂O₃ and (Zr_0.8Ti_0.2)TiO₄ ceramics with Teflon and alumina as supports were measured. The results show that the τ_f values of the same resonator with above supports are different, and the measured variation between them is more than 3 ppm/˚C. Using the concept of τ_f0, the variation is less than 2 ppm/˚C.

With appropriate geometry configurations, bistatic Synthetic Aperture Radar (SAR) can break through the limitations of monostatic SAR on forward-looking imaging. Thanks to such a capability, bistatic forward-looking SAR (BFSAR) has extensive potential applications. For the focusing problem of BFSAR, wavenumber-domain algorithm is accepted as the ideal solution. However, in practical application, the processing is limited because of its inability to combine the range-dependent motion compensation (MoCo). To cope with such a problem, an extended wavenumber-domain algorithm for BFSAR is derived in this paper. By modifying the reference function and mapping relationship in frequency interpolation, the extended wavenumber-domain algorithm of BFSAR integrates a two-step motion compensation. Simulation results verify the effectiveness of the proposed method.

To effectively simplify system structure and improve power density and efficiency, a design for a motor/generator suitable for flywheel energy storage system (FESS) is proposed. The machine is an outer-rotor and coreless-stator-type bearingless permanent magnet synchronous motor (BPMSM) with a Halbach array. Firstly, the operation principle of the outer-rotor BPMSM is described. Then, the structure and performance of the Halbach permanent magnet (PM) array are analyzed. The airgap magnetic field, back-EMF, suspension force, unilateral magnetic pull force and electromagnetic torque are calculated and analyzed by the finite element analysis (FEA). Finally, it is verified that the magnetic field of the suspension force windings increases the rotor eddy current loss by transient FEA coupled with external circuit. The rotor eddy current losses of BPMSM with different structures are compared. The comparison results show that the rotor eddy current loss of the coreless-stator-type BPMSM with Halbach array is the lowest. The simulation results verify the theoretical analysis and structure design, which can provide reference for the application of the motor in the FESS.

This paper presents an analytical calculation of magnetic field and electromagnetic performances of 3-, 5-, 7-, 9-, 11-phases cage rotor induction machines in healthy, broken bars and open phase's conditions. This model is formulated to consider all types of multi-phase/multipoles windings and used for the identification of electrical equivalent circuit (EEC) parameters. It's based on the subdomain model and the resolution of Poisson's, Laplace's, and Helmholtz's equations in each subdomain issued from Maxwell equations using the method of separation of variables and Fourier series when the machines are fed with sinusoidal current and voltage. The developed analytical model permits the calculation of magnetic field distribution, eddy current, circuit model parameters, and unbalanced magnetic radial force due to broken bars, electromagnetic torque and absorbed stator current. A comparative analysis between the studied five multi-phases machines is done with considering identical power rate. The analytical results are validated by those issued from the finite-element method (FEM).

In this paper, four novel wide-band dual tapered slot (DTS) microstrip antennas (MSAs) are proposed for X-Band Satellite Communications (SATCOM) applications. Three of them have stripline feeds between SMA connector and tapering profile, whereas the fourth one omits the stripline feed. Each antenna consists of two microstrip lines on each side of an FR-4 substrate, fed with a coaxial connector from one face. Towards the edges, the distance between conductors is increasing gradually. The aim of this study is to design receiver antennas capable of operating in X-Band Satellite Communications (7250-7750 MHz) range and investigate the effects of tapering profiles on the performance. For this purpose, each antenna is defined in terms of parameters, and the optimum values for all parameters are calculated using High Frequency Structure Simulator (HFSS) software. The antennas are simulated and practically fabricated. Results show good agreement between simulations and measurements. The antennas have impedance bandwidth of 380 MHz centered at 7448 MHz for dual linearly tapering, 540 MHz centered at 7434 MHz for dual circularly tapering, 900 MHz centered at 7555 MHz for dual exponentially tapering, within the aimed Super High Frequency (SHF) range. Also, the designed fourth antenna having dual circularly tapering without the stripline feed has a bandwidth of 1150 MHz centered at 7676 MHz. It is proposed that taper profile affects bandwidth, gain, radiation efficiency, radiation pattern and antenna dimensions.

This article focuses on the development of a high gain, broadband, circularly polarized Electromagnetic Band Gap (EBG) antenna operating at 60 GHz. The designed antenna is configured with a superstrate based on a frequency selective surface (FSS) placed in front of a cross dielectric resonator antenna (XDRA), installed into a ground plane, which acts as an excitation source. A fast Leaky-Wave approach based on transverse equivalent network (TEN) is used to deduce analytical radiation patterns formulas of the proposed antenna. The proposed analytical model was implemented and verified by a comparison with both numerical and experimental results. The reported results showed very satisfactory performances with an achievable impedance bandwidth (S₁₁< -10 dB) of 11.7% from 56 to 63 GHz, an axial-ratio bandwidth (AR<3 dB) of 5.4% from 58.9 to 62.1 GHz and a stable gain of 16.7 dBi within the passband. A good agreement among analytical, numerical and measured results is successfully achieved and falls well within initially set specifications.

This paper presents 2-way Power Divider (PD) for Ultra-Wideband (UWB) applications. The proposed power divider is realized using two cascaded sections of Wilkinson Power Divider (WPD) of equal characteristic impedances and unequal electrical lengths with inserted open stub to improve matching, isolation and to broaden the bandwidth. It is proved analytically using the ``Even Odd Mode'' analysis method and the ABCD matrix to obtain exact closed-form design equations. A detailed design methodology is introduced to facilitate the implementation without needing CAD optimization. To verify the proposed design methodology, a 2-way power divider is designed, fabricated on a Rogers RT/Duroid 5880 substrate and compared to other published 2-way microstrip power dividers. Measured data show good agreement with Electromagnetic (EM)-Circuit Co-Simulation, which proves the design equations and methodology. The proposed planar 2-way PD achieves an isolation ≥ 13.5 dB, input return loss ≥10 dB, output return loss ≥14.5 dB and exceeded insertion loss ≤ 0.9 dB (over the -3 dB splitting ratio) through the whole UWB range from 3.1 GHz to 10.6 GHz. Furthermore, it has a compact area of 22 mm × 15 mm, which provides 50% enhancement over similar microstrip PD circuits while achieving better isolation and matching.

In this letter, a new model of antenna with Jerusalem crosses (JC) as fractal slots for circular polarization applications is designed. The proposed slot antenna has a fractal cross formation with four Jerusalem crosses (JC) to achieve wide bandwidth and a compact size as well as circular polarization. A T-shaped feed line is implemented in the proposed antenna for improving the bandwidth while the interaction of the feed line with cross-shaped slots makes circular polarization. The proposed antenna shows bidirectional pattern and bandwidth at 2.42-3.0 GHz with VSWR<2, which can be used in Wi-Fi and Bluetooth applications with a gain of 3.5 dBi. The proposed fractal antenna size is 40×40 mm, and it is designed and fabricated on an FR-4 low-cost substrate with thickness of 1.6 mm. It is simulated by HFSS full wave software. In addition, the experimental results are presented and compared with the simulation for VSWR, radiation pattern and axial ratio.

An efficient algorithm based on high-order cumulant is addressed for the scenarios where both far-field and near-field narrow-band signals may exist synchronously. The first matrix built by four-order cumulant is utilized to estimate the two dimensional direction-of-arrivals (DOAs) using the orthogonal projection matrix of the signal subspace and the virtual steering matrix. Then, the second matrix built by four-order cumulant is decomposed to get the noise subspace using the eigen decomposition. Meanwhile, a virtual steering matrix is used to distinguish far-field signals (FFSs) from near-field signals (NFSs). And one-dimensional MUSIC algorithm is used to estimate the range of the NFSs. Compared to the TSMUSIC, the proposed algorithm can provide high resolution for the DOAs. In addition, there is higher accuracy for the DOA of NFS in the proposed algorithm than that in TSMUSIC and in TSMD. Simulation results are carried out to certify the performance of the proposed algorithm.

The effect of a substantial increase of the Faraday rotation angle has been investigated in a symmetrical resonator structure, which is represented by a one-dimensional photonic crystal with dielectric Bragg mirrors and a magnetically active layer placed between mirrors. In the numerical analysis, the parameters of a pure yttrium iron garnet at two wavelengths - 1.15 μm and 1.3 μm have been used. The increase in the Faraday rotation angle is caused by not only an increase of the magnetic layer thickness, but also a symmetrical increase in the number of Bragg mirrors periods.

In this paper, we introduce an efficient algorithm to analyze metamaterials, which can be finite periodic structures with tightly coupling between nearby cells. Firstly, the algorithm, based on method of moments (MoM), uses hybrid volume-surface integral equation (VSIE) to analyze composite dielectric-conductor objects. Then, the characteristic basis function method (CBFM) and precorrected-fast Fourier transform (p-FFT) algorithm are combined to accelerate the calculation of equations, based on which, metamaterials composed of connected periodic cells can be analyzed efficiently.

Multipactor effect is studied in a hollow elliptical waveguide carrying two orthogonal polarization modes, i.e., the fundamental (TE_c11) and the second (TE_s11) elliptical waveguide modes. The introduction of a modal equivalent voltage allows defining the standard axial ratio, which characterizes each polarization state of the problem. The RF breakdown threshold is determined as a function of the axial ratio for various amplitudes and phases of the two elliptical modes. In particular, the effect of the second mode on the RF breakdown threshold of the fundamental mode is studied. The simulations are carried out for different values of the eccentricity of the ellipse eccentricity.

This paper presents a design of wideband and low-profile linear array of H-plane horn antennas. In order to construct the linear array in H-plane, the aperture size of the horn antenna in the H-plane should be comparable with one wavelength in the free space, which leads to a poor impedance matching especially in the lower frequency range. The approach to the problem is removing the side walls of the flare part of the antennas. The array is fed by a wideband 4-way ridged SIW power divider. The designed array operates from 5.6 GHz to 18 GHz for VSWR 2.5 and exhibits stable radiation beam with a narrow beam-width in H plane over the same frequency rang while retaining the antenna array height of only 4 mm (0.17λ₀ at the center frequency). The designed array is fabricated and tested. It is observed that measured results agree well with simulated ones.

In this paper, materials frequently used in high-speed (HS) electrical machines are assessed. Highspeed permanent magnet synchronous machines with a special tooth-coil topology serve as an example for the assessment. The lamination and rotor sleeve materials are compared taking into account their price, per unit losses, resistivity, and other factors. The resulting tables provide the electrical machine designer with a means to enhance the HS machine performance at low costs.

We examine the effect of alignment errors on the performance of a frequency-diverse imaging system composed of metamaterial apertures. In a frequency-diverse imaging system, a sequence of distinct radiation patterns, indexed by frequency, provides measurements of the spatial content of a scene. This set of measurements can then be used to obtain a high-fidelity estimate of the scene using computational imaging techniques. As with any computational imaging system, realizing the full potential of the frequency-diverse system requires accurate characterization of the complex radiation patterns. This characterization entails precise knowledge of the locations and orientations of the transmitters and receivers; any discrepancy between the modeled and actual locations will introduce phase error and degrade the quality of image reconstructions. Here, we study the effect of various misalignment errors on the performance of a sparse, bistatic, frequency diverse imaging system and provide an estimate on the levels of error within which the frequency-diverse apertures can reconstruct high quality images. Depending on the misalignment type (i.e., displacement, rotation) and direction the phase error can change significantly. As a result, for instance, we show that the imaging system is significantly less sensitive to cross-range displacement errors than to range displacement errors. We also show that the displacement errors are reduced for larger systems comprising many sub-apertures, due to the reduced averaged phase error. We find the impact of rotational errors is small compared to that of the displacement errors. However, as the sub-aperture size increases, rotational errors become more pronounced, becoming severe for larger sub-apertures with multiple feeds.

A compact monopole antenna with broadband circular polarization for global navigation satellite system (GNSS) applications is presented in this paper. The proposed antenna comprises a simple tilted radiator fed by 50-Ohm microstrip line and an improved ground plane. By embedding two isosceles right triangular slits and introducing an isosceles right triangular perturbation in the ground plane, the circularly polarized (CP) performance can be improved significantly. The impedance and circular polarization characteristics are studied by simulation and measurement. With a compact size of 79×79×1.5 mm³ for the fabricated antenna, a measured 10-dB return loss bandwidth of 35.6% (1.13-1.62 GHz) and a 3-dB AR bandwidth of 35.4% (1.14-1.63 GHz) can be achieved.

This paper presents a novel, dual, three-stepped-trident, planar, monopole antenna for ultra-wideband applications. The planar trident type antenna is designed, simulated, and fabricated. Its impedance bandwidth, radiation pattern and gain performances were measured. This antenna operates in the ultra-wideband from 3.0 GHz to 12.15 GHz. The maximum gain of this antenna design is 5.5 dBi. Measurements confirm the simulated results over the frequency of operation.

Energy conservation is an important consideration in wave scattering and transmission from random rough surfaces and is particularly important in passive microwave remote sensing. In this paper, we study energy conservation in scattering from layered random rough surfaces using the second order small perturbation method (SPM2). SPM2 includes both first order incoherent scattering and a second order correction to the coherent fields. They are combined to compute the total reflected and transmitted powers, as a sum of integrations over wavenumber k_x, in which each integration includes the surface power spectra of a rough interface weighted by an emission kernel function (assuming the roughness of each interface is uncorrelated). We calculate the corresponding kernel functions which are the power spectral densities for one-dimensional (1D) surfaces in 2D scattering problems and examine numerical results for the cases of 2 rough interfaces and 51 rough interfaces. Because it is known that the SPM when evaluated to second order conserves energy, and it can be applied to second order for arbitrary surface power spectra, energy conservation can be shown to be satisfied for each value of k_x in the kernel functions. The numerical examples show that energy conservation is obeyed for any dielectric contrast, any layer configuration and interface, and for arbitrary roughness spectra. The values of reflected or transmitted powers predicted, however, are accurate only to second order in surface roughness.

A novel miniaturized design of UWB monopole antenna is presented and investigated for oil pipeline imaging. In the proposed antenna, an annular-ring shaped radiating patch, slotted ground plane and a feed-line embedded with a semicircular stub are used to enhance the bandwidth. The slotted ground-plane has two extended rectangular strips on its two sides to excite the lower frequency resonance. The proposed antenna design exhibits an enhanced bandwidth of 22 GHz from 3 to 25 GHz (for return loss <10 dB) which provides a wide usable fractional bandwidth of more than 157% with a compact size of 15 mm×12 mm. Simulated and measured results are discussed to validate the proposed antenna design with enhanced wide bandwidth performance.

This paper presents a comprehensive analysis of the roadway powering system for electric vehicles (EVs) and proposes a design from the perspective of power track design, integration, and powering control strategy, aiming to ensure the charging power and persistence, enhance the control flexibility, and reduce the construction cost. 1) A novel design scheme is first proposed to determine the length and number of turns for power tracks by investigating the power supply-and-demand and the loss. 2) A novel evaluation index, namely the magnetic distribution variance, is proposed to determine the gap between adjacent tracks, which can effectively produce evenly-distributed energy field, thus improving the dynamic charging performance for EVs. 3) A sectional powering control strategy is proposed to implement a cost-saving and flexible roadway powering system. Lastly, the simulated and experimental results show that the exemplified prototype can achieve the transmission power 50W over the distance of 200 mm, which verifies the proposed EV dynamic charging system with the salient advantages of the constant energization, flexible power control, and cost saving.